Overhead sectional garage doors or the like are typically provided with rollers that ride in a track system usually carried by a horizontally oriented angle member extending inwardly from the door frame. When the door is in the closed position, the rollers reside in opposed vertically oriented tracks, and when moved to an open position, the rollers travel up the vertical tracks, through opposed transitional tracks, and into opposed generally horizontally oriented tracks.
Traditionally, the transitional tracks are of a circular radius of curvature to make the ninety degree transition from the vertical tracks to the horizontal tracks. These transitional tracks may be a separate piece, having their ends attached to the vertical and horizontal tracks, or they may be incorporated into either the vertical tracks or the horizontal tracks thereby creating a two-piece system instead of a three piece system. In some instances, the track system may be formed as one piece incorporating the vertical tracks, the horizontal tracks and the transitional tracks.
The radius of the typical prior art transitional tracks generally varies between eight inches and thirty inches. Radii toward the upper end of the range are desirable because such provides for a smoother operation of the door. However, such requires more headroom. In situations where there is minimal headroom, transitional tracks with a short radius must be utilized to the sacrifice of smooth operation.
As a compromise, attempts have been made at providing a one piece track system which includes the vertical tracks, the horizontal tracks, and a transitional track portion having two radii of curvature. However, in order to accommodate for low headroom environments and yet still satisfactorily operate, the radii of curvature need to be quite different, that is, one of the radii needs to be substantially smaller than the other radii, and such cannot be readily accomplished in one piece.
Thus, the need exists for a track system which is not plagued by these problems of the prior art.